An apparatus has heretofore been developed and proposed to successively make plastic bags each of which includes panel portions, side gusset portions and a bottom gusset portion, as disclosed in U.S. Pat. No. 7,331,917. Each of the side gusset portions has opposite end portions at one of which an auxiliary gusset portion is formed. The bottom gusset portion is combined with the auxiliary gusset portion. The plastic bag is called a rectangular bottom bag.
In the apparatus, webs of panel material are superposed on each other and fed longitudinally thereof and intermittently. The panel portions are formed by the webs of panel material. A sheet of side gusset material is folded into halves, superposed into two layers and then supplied to and interposed between the webs of panel material to extend widthwise thereof whenever the webs of panel material are fed intermittently. The sheet of side gusset material has opposite end portions. The side gusset portion is formed by the sheet of side gusset material.
In addition, one of the webs of panel material is temporarily fixed to one of the layers of side gusset material while the other web of panel material is temporarily fixed to the other layer of side gusset material at one of the end portions of side gusset material after the sheet of side gusset material is interposed. Furthermore, the apparatus includes panel material guide means by which the webs of panel material are guided to be folded respectively when being fed. One of the webs of panel material is folded along a longitudinal folded line when being fed to make the webs of panel material open and make an open surface formed on the webs of panel material. One of the layers of side gusset material is pulled by one of the webs of panel material to be folded along the longitudinal folded line to make the layers of side gusset material open along with the auxiliary gusset portion and make an open surface formed on the layers of auxiliary gusset portion. The other web of panel material is folded along a longitudinal folded line when being fed to make a folded portion formed in the other web of panel material and superposed on the open surfaces of panel material and auxiliary gusset portion. The folded portion is used as a web of bottom gusset material by which the bottom gusset portion is formed.
In addition, the web of bottom gusset material or the folded portion is folded back along a longitudinal folded back line and into halves when being fed. At the same time, one of the webs of panel material is unfolded so that the web of bottom gusset material can be interposed between the webs of panel material. The web of bottom gusset material and the auxiliary gusset portion are then heat sealed with each other while the webs of panel material and the sheet of side gusset material are heat sealed with each other widthwise of the webs of panel material whenever the webs of panel material are fed intermittently. The web of bottom gusset material and at least one of the webs of panel material are heat sealed with each other longitudinally of the webs of panel material whenever the webs of panel material are fed intermittently.
However, the apparatus has not only to make one of the webs of panel material folded, make the open surfaces formed and make the web of bottom gusset material superposed but also to make the web of bottom gusset material folded back and make one of the webs of panel material unfolded so that the web of bottom gusset material can be interposed between the webs of panel material. Accordingly, the panel material guide means must be complicated in structure. It is therefore desired to successively make the rectangular bottom bags in a way different from the apparatus.
It is therefore an object of the invention to provide an apparatus for successively making plastic bags each of which includes panel portions, side gusset portions and a bottom gusset portion, in a way different from the prior art.
Another object is to provide the apparatus which has only to make one of the webs of panel material folded, make the open surfaces formed and make the web of bottom gusset material superposed and has neither to make the web of bottom gusset material folded back nor to make one of the webs of panel material unfolded.